Because of their excellent properties, a great demand for polyamide resins as engineering plastics is expected. However, the polyamide resins are not sufficient in flexibility, low-temperature impact resistance, resistance to water absorption and resistance to saline solutions, and improvements of these properties have been variously studied. If the polyamide resins are improved in the flexibility and the low-temperature impact resistance, there is expected wide use application of sporting goods such as ski shoes, sports shoes and industrial parts such as automobile parts, oil tubes, flexible tubes and air hoses, and a demand for such resins becomes great.
For improving the flexibility, the water resistance such as resistance to water absorption or the resistance to saline solutions of the polyamide resins, a method of adding an ethylene/.alpha.,.beta.-unsaturated monocarboxylic acid copolymer neutralized product (ionomer resin) to a polyamide resin is proposed in Japanese Patent Laid-Open Publications No. 80014/1978, No. 167751/1981, No. 109247/1981 and No. 157451/1981.
However, the polyamide resin compositions proposed in these publications are poor in the improvement of impact resistance such as Izod impact strength, particularly impact resistance at low temperatures, though they can be improved in the water resistance such as resistance to water absorption and resistance to saline solutions.
For improving the impact resistance such as Izod impact resistance of the polyamide resins, a method of adding an ethylene/.alpha.-olefin copolymer grafted with an .alpha.,.beta.-unsaturated carboxylic acid to a polyamide resin is proposed in, for example, Japanese Patent Publications No. 12546/1967 and No. 44108/1980 and Japanese Patent Laid-Open Publication No. 9662/1980.
However, the polyamide resin compositions proposed in these publications are insufficient in the flexibility and the impact resistance at low temperatures. Moreover, these polyamide resin compositions are deteriorated in the moldability at same molding processes.
For improving particularly the flexibility of the polyamide resins, a method of adding an ethylene/propylene copolymer or an ethylene/1-butene copolymer grafted with an .alpha.,.beta.-unsaturated carboxylic acid to a polyamide resin in an amount of more than 2/3 times and not more than 6 times as much as the amount of the used polyamide resin is proposed in, for example, Japanese Patent Publication No. 13379/1987.
However, the polyamide resin composition proposed in this publication is still insufficient in the impact resistance at low temperatures and has a serious problem of deteriorated moldability, though it shows sufficient flexibility.
Under the circumstances, the advent of a polyamide resin composition which shows good moldability and can provide a molded article excellent in flexibility, low-temperature impact resistance, resistance to water absorption and resistance to saline solutions has been heretofore desired.
The present invention is intended to solve such problems associated with the prior art technique as mentioned above, and an object of the invention is to provide a polyamide resin composition which shows good moldability and can give a molded article excellent in flexibility, low-temperature impact resistance, resistance to water absorption and resistance to saline solutions.